Such positioning devices are used in particular to drive exhaust gas recirculation valves, but they may also be used in waste gate valves, butterfly valves or as VNT actuators.
Various valves with positioning devices or similar positioning devices are known, wherein an electric motor serves as the drive unit whose drive shaft is coupled with eccentrics of various types, the motion of the eccentrics being converted, via different coupling mechanisms, into a linear motion of a valve rod serving as an adjusting element.
EP 1 319 879 A1 describes a valve driven by an electric motor, wherein an output shaft is arranged eccentrically with respect to a drive shaft, a roller being provided rotatably on the output shaft and traveling in a slot of a coupling element. The roller is spring-biased in one direction. The traveling path of the coupling element slot provided for the roller is perpendicular to the direction of movement of the coupling element. The development of the force-stroke curve of this element is thus fixed.
DE 102 21 711 A1 describes a similar valve wherein two eccentrics are coupled with each other. In this design, the slot that serves as a traveling path for a ball bearing is also designed as a straight line that extends perpendicularly to the direction of movement. It is again not possible to provide special required force-stroke curves during the actuation of the valve with sufficient variability.
A valve driven by an electric motor is also described in EP 1 378 655 A2, wherein a rotating member comprises two opposite slots in which a rod is guided which in turn is connected with a valve rod. The slot may here be configured as a defined curve. With this design, it is possible to set a defined effort for the adjustment of the valve as a direct function of the stroke. The required structural space is rather large, as is the number of components needed.